ICOS Mediates the Generation and Function of CD4+CD25+Foxp3+ Regulatory T Cells Conveying Respiratory Tolerance

Costimulatory molecules like ICOS are crucial in mediating T cell differentiation and function after allergen contact and thereby strongly affect the immunologic decision between tolerance or allergy development. In this study, we show in two independent approaches that interruption of the ICOS signaling pathway by application of a blocking anti-ICOSL mAb in wild-type (WT) mice and in ICOS(-/-) mice inhibited respiratory tolerance development leading to eosinophilic airway inflammation, mucus hypersecretion, and Th2 cytokine production in response to OVA sensitization. Respiratory Ag application almost doubled the number of CD4(+)Foxp3(+) regulatory T cells (Tregs) in the lung of WT mice with 77% of lung-derived Tregs expressing ICOS. In contrast, in ICOS(-/-) mice the number of CD4(+)CD25(+)Foxp3(+) Tregs did not increase after respiratory Ag application, and ICOS(-/-) Tregs produced significantly lower amounts of IL-10 than those of WT Tregs. Most importantly, in contrast to WT Tregs, ICOS(-/-) Tregs did not convey protection when transferred to "asthmatic" recipients demonstrating a strongly impaired Treg function in the absence of ICOS signaling. Our findings demonstrate a crucial role of ICOS for the generation and suppressive function of Tregs conveying respiratory tolerance and support the importance of ICOS as a target for primary prevention strategies.     

Relevance of exocytotic glutamate release from retinal glia

Glial cells release molecules that influence brain?development, function, and disease. Calcium-dependent exocytosis has been proposed as potential release mechanism in astroglia, but the physiological relevance of "gliotransmission" in?vivo remains controversial. We focused on the impact of glial exocytosis on sensory transduction in the retina.?To this end, we generated transgenic mice to block exocytosis by Cre recombinase-dependent expression of the clostridial botulinum neurotoxin serotype?B light chain, which cleaves vesicle-associated membrane protein 1-3. Ubiquitous and neuronal toxin expression caused perinatal lethality and?a reduction of synaptic transmission thus validating transgene function. Toxin expression in Müller cells inhibited vesicular glutamate release and impaired glial volume regulation but left retinal histology and visual processing unaffected. Our model to study gliotransmission in?vivo reveals specific functions of exocytotic glutamate release in retinal glia.     

3-Decanol in the haemolymph of the hermit crab Clibanarius vittatus signals shell availability to conspecifics

Hermit crabs with poor fitting shells are chemically attracted to dying gastropods and conspecifics where a shell may become available. For land hermit crabs, the shell cue is a volatile compound found in the haemolymph. Based on this knowledge, we tested the hypothesis that shell investigation behavior in aquatic hermit crabs, the ancestral predecessors of terrestrial hermit crabs, is also triggered by volatile cues. Volatile compounds from haemolymph of Clibanarius vittatus and Pagurus pollicaris and brachyuran decapod crustaceans were purged from a water-haemolymph solution, trapped in seawater and tested for induction of shell investigation behavior with juvenile C. vittatus. Only volatiles from C. vittatus haemolymph stimulated shell investigation. Volatile compounds were isolated from haemolymph by headspace solid-phase microextraction (SPME) and analyzed by coupled gas chromatography-mass spectrometry (GC-MS). Two prominent compounds were identified, 3-decanol, which was unique to C. vittatus haemolymph, and 2-ethyl-1-hexanol, which was present in the haemolymph of all 4 crustacean species. In shell investigation bioassays, 3-decanol from C. vittatus haemolymph stimulated shell investigation behavior, while 2-ethyl-1-hexanol did not. In bioassays with synthetic 1-, 2-, 4-, and 5-decanol, shell investigation behavior was evoked by 1-decanol, 5-decanol and 3-undecanol. There was no response to 2- and 4-decanol. The response of C. vittatus to volatile shell cues supports the hypothesis that volatile cue detection evolved prior to the occupation of terrestrial niches by crustaceans.     

Noninvasive,In Vivo Assessment of Mouse Retinal Structure Using Optical Coherence Tomography

Background

Optical coherence tomography (OCT) is a novel method of retinal in vivo imaging. In this study, we assessed the potential of OCT to yield histology-analogue sections in mouse models of retinal degeneration.

Methodology/Principal Findings

We achieved to adapt a commercial 3^rd generation OCT system to obtain and quantify high-resolution morphological sections of the mouse retina which so far required in vitro histology. OCT and histology were compared in models with developmental defects, light damage, and inherited retinal degenerations. In conditional knockout mice deficient in retinal retinoblastoma protein Rb, the gradient of Cre expression from center to periphery, leading to a gradual reduction of retinal thickness, was clearly visible and well topographically quantifiable. In Nrl knockout mice, the layer involvement in the formation of rosette-like structures was similarly clear as in histology. OCT examination of focal light damage, well demarcated by the autofluorescence pattern, revealed a practically complete loss of photoreceptors with preservation of inner retinal layers, but also more subtle changes like edema formation. In Crb1 knockout mice (a model for Leber''s congenital amaurosis), retinal vessels slipping through the outer nuclear layer towards the retinal pigment epithelium (RPE) due to the lack of adhesion in the subapical region of the photoreceptor inner segments could be well identified.

Conclusions/Significance

We found that with the OCT we were able to detect and analyze a wide range of mouse retinal pathology, and the results compared well to histological sections. In addition, the technique allows to follow individual animals over time, thereby reducing the numbers of study animals needed, and to assess dynamic processes like edema formation. The results clearly indicate that OCT has the potential to revolutionize the future design of respective short- and long-term studies, as well as the preclinical assessment of therapeutic strategies.     

Hygrochastic capsule dehiscence supports safe site strategies in New Zealand alpine Veronica (Plantaginaceae)

Background and Aims

Hygrochasy is a capsule-opening mechanism predominantly associated with plants in arid habitats, where it facilitates spatially and temporally restricted dispersal. Recently, hygrochastic capsules were described in detail for the first time in alpine Veronica in New Zealand. The aim of the present study was to investigate whether hygrochastic capsules are an adaptation of alpine Veronica to achieve directed dispersal to safe sites. We expect that by limiting dispersal to rainfall events, distances travelled by seeds are short and confine them to small habitat patches where both seedlings and adults have a greater chance of survival.

Methods

Dispersal distances of five hygrochastic Veronica were measured under laboratory and field conditions and the seed shadow was analysed. Habitat patch size of hygrochastic Veronica and related non-hygrochastic species were estimated and compared.

Key Results

Dispersal distances achieved by dispersal with raindrops did not exceed 1 m but weather conditions could influence the even distribution of seeds around the parent plant. Compared with related Veronica species, hygrochastic Veronica mostly grow in small, restricted habitat patches surrounded by distinctly different habitats. These habitat patches provide safe sites for seeds due to their microtopography and occurrence of adult cushion plants. Non-hygrochastic Veronica can be predominantly found in large habitats without clearly defined borders and can be spread over long distances along rivers.

Conclusions

The results suggest that hygrochasy is a very effective mechanism of restricting seed dispersal to rainfall events and ensuring short-distance dispersal within a small habitat patch. It appears that it is an adaptation for directed dispersal to safe sites that only exist within the parent habitat.     

PARP1 gene knock-out increases resistance to retinal degeneration without affecting retinal function

Retinitis pigmentosa (RP) is a group of inherited neurodegenerative diseases affecting photoreceptors and causing blindness in humans. Previously, excessive activation of enzymes belonging to the poly-ADP-ribose polymerase (PARP) group was shown to be involved in photoreceptor degeneration in the human homologous rd1 mouse model for RP. Since there are at least 16 different PARP isoforms, we investigated the exact relevance of the predominant isoform - PARP1 - for photoreceptor cell death using PARP1 knock-out (KO) mice. In vivo and ex vivo morphological analysis using optic coherence tomography (OCT) and conventional histology revealed no major alterations of retinal phenotype when compared to wild-type (wt). Likewise, retinal function as assessed by electroretinography (ERG) was normal in PARP1 KO animals. We then used retinal explant cultures derived from wt, rd1, and PARP1 KO animals to test their susceptibility to chemically induced photoreceptor degeneration. Since photoreceptor degeneration in the rd1 retina is triggered by a loss-of-function in phosphodiesterase-6 (PDE6), we used selective PDE6 inhibition to emulate the rd1 situation on non-rd1 genotypes. While wt retina subjected to PDE6 inhibition showed massive photoreceptor degeneration comparable to rd1 retina, in the PARP1 KO situation, cell death was robustly reduced. Together, these findings demonstrate that PARP1 activity is in principle dispensable for normal retinal function, but is of major importance for photoreceptor degeneration under pathological conditions. Moreover, our results suggest that PARP dependent cell death or PARthanatos may play a major role in retinal degeneration and highlight the possibility to use specific PARP inhibitors for the treatment of RP.     

High-frequency stimulation of the subthalamic nucleus enhances striatal dopamine release and metabolism in rats

High-frequency stimulation of the subthalamic nucleus is believed to exert its main effects via the basal ganglia output structures. Previously, we have shown a concomitant increase in striatal dopamine (DA) metabolites in normal and 6-hydroxydopamine-lesioned rats. The present study was designed to determine whether this increase in striatal DA metabolites reflects enhanced intraneuronal DA turnover or, alternatively, is due to increased DA release with subsequent rapid and efficient reuptake and/or metabolism. Thus, high-frequency stimulation of the subthalamic nucleus was performed in normal rats after inhibition of DA reuptake, metabolism or DA depletion. Extracellular levels of striatal DA and its metabolites were assessed using microdialysis. Our data suggest that subthalamic high-frequency stimulation increases striatal DA release and activates independent striatal DA metabolism. Since such changes could be triggered by modification of either the activity or the gene expression of the rate-limiting enzyme tyrosine hydroxylase, an activity assay and RT-PCR of striatal and nigral samples were performed. Subthalamic stimulation increased striatal tyrosine hydroxylase activity without affecting gene expression. We, therefore, conclude that the application of subthalamic high-frequency stimulation could partially compensate for the DA deficit by inducing increased striatal DA release and metabolism.     

On the localization of enzymes related to flavonoid metabolism in sections and tissues of oat primary leaves

During growth of the primary leaves of Avena sativa L., the distribution of extractable L-phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) and chalcone-flavanone isomerase (CFI, EC 5.5.1.6) activities in distinct leaf sections (top section, medium section and meristematic basal section) and in the epidermal and mesophyll tissues were investigated in relation to C-glycosylflavone accumulation. Characteristic changes have been observed in the levels of PAL and CFI activities within the three leaf sections, depending upon their stage of development. An increase in both enzyme activities accompanies a strong flavone accumulation in the section of the leaf that derives from the basal meristem. Highest specific PAL activity is localized in the meristem itself, which is poor in both flavones and CFI activity. Total flavone accumulation was found to be nearly the same in all three leaf tissues, lower and upper epidermis and mesophyll. Similarly, PAL activity is distributed about equally in these tissues in young leaves; in older ones, activity is relatively higher in the lower leaf epidermis. In contrast, CFI is found to be localized almost entirely in the mesophyll and not in the epiderms. Therefore the question arises whether CFI is involved at all in flavone metabolism and whether it may represent, as a marker enzyme, the localization of other specific C₁₅-enzymes of the flavonoid biosynthetic pathway in oat primary leaves.Abbreviations PAL L-phenylalamine ammonia lyase - CFI chalcone-flavanone isomerase     

The Arctic sponge Haliclona viscosa as a source of a wide array of 3-alkyl pyridine alkaloids

The Arctic sponge Haliclona viscosa has proven to be a promising source for 3-alkyl pyridinium and 3-alkyl tetrahydropyridine alkaloids (3-APAs). H. viscosa was the origin of the first cyclic monomeric 3-APA (haliclocyclin F), the first cyclic trimeric 3-APA (viscosamine C), the first dimeric 3-APA amino acid adduct (viscosaline C), and the first 3‐alkyl tetrahydropyridine alkaloids with saturated alkyl chains (haliclamines C and D). This review focuses on the challenging structure elucidations of 3-APAs isolated from H. viscosa using a combination of NMR spectroscopy and mass spectrometry.